Electric revolution-meter for internal-combustion engines.



J. KIRBY-E ELEGTRIC REVOLUTION METER FOR INTERNAL COMBUSTION ENGINES.

APPLICATION FILET) JAN-26. I917- Pafented Oct. 2-, 1917.

4 TTORNEYS ELnc'rnIc nnvorU'rIon-Mn'rnn To all whom it may concern:

7 Be it known that I, J onn KIRBY, a sub ject of the King of Great Britain, and a resident of'the city of New York,'borough New York, have invented a new and 1111- proved Electric Revolution-l/leter for Internal-Combustion Engines, of which the following is a full, clear, and exact descrip tion.

This invention relates to a revolution meter especially adapted for ind cating the revolut1ons per minute of an-mternal combustion engine, the meter being designed for use in connection with automobiles.

A more-specific object of the invention is the provision of an instrument of the class described which is adapted to b3 connected with-the ignition circuit of an automobile so as to indicate by the rapidity of the current impulses the revolutions of the engine,

the scale of the device being calibrated ac-.

cording to whether the instrument is used in connection with a single or multiple cylinder eng ne.

A specific provision of posed of two oppositely wound coils normally balanced and connected in shunt'withv each other in an ignition circuit of an engine,'there being in series with the respective coils -a reactance and a resistance both of the same ohmic value, whereby upon cer-' tain low speeds of the engine there will be no magnetic unbalance of the coils and the armature will not move, but under high speeds the reactance retards the flow of current so that'the coils become unbalanced magnetically and the armature will move and carry with it the needle, which in connection with the dial will indicate the speed of the engine.

With such objects in view, and others which willappear as the description proceeds, the invention comprises various novel features of construction and arrangement of parts which will be set forth with particularity in the following description and claim appended hereto.

In the accompanying drawings, which illustrate one embodiment of the invention and wherein similar characters of reference indicate corresponding parts in all the views, I A a Specification of Letters ma.

ture-carrying object of the invention is the an energizing. element comsins PATENT. onnicn .ioniv RIB-BY, or NEW'YORK, N. Y. i

FOR INTERNAL-CQMBUSTION ENGINES.

ment

Patented.0ct. 2, 191%; Application filed January as, 1917. Serial int-"144,797.

Figurelv is a sectionalview of the instru-v Fig.j 2- is frontfview with "a portion broken away; and of.Manhattan, 1n thecounty andState of Fig. 3'is' a diagrammatic view. v

. Referring to the drawings, A designates".

a casing of any suitable construction" which is mounted a dial plate 1 over which moves a needle or hand 2 that is driven from} an armature-carrying shaft 3 through a' gear wheel 4 and pinion '5, the latter being mounted on the needlefshaft 6, to'which is connected the needle-returning spring 7 form with its axis to one side of the armashaft 3. The energizing winding is made up of two coils 10 and 11 oppositely Wound so that when current of equal strength flows through both coils they will neutralize each other and produce no magnetic efi'ect. When the magnetic balance of the two coils is disturbed the armature.-

which are of the same number of turns but f and-break device 13 and source of current 14 are shown.. The two coils 10 and 11 of the instrument are connected in parallel relation with one side of the ignitioncircuit,

and in series with the coil 10 is a resistance.

and in series with theother coil is. a

reactance. 16, both of which are connected Withthe other side of the ignition circuit. In other words, there are two shunts formed in the ignition circuit which are of the same ohmic value and which are normally magneticallybalanced. The speed of the engine having a-definite relation to the makeand-break of the ignition circuit, it can be determined by means of the armature, under the magnetic influence of the winding 9., "At low speeds substantially the same amount of current flows through both coils -10 and 11, but at high speeds the reactance cuts down the flow of current through the coil 11, so that the two sections of the winding 9 become unbalanced and the armature will move and cause the needle to indicate the speed at which the engine crank shaft is revolving. In-the diagra'm shown in Fig.

3 an ignition circuit is adapted for a single cylinder engine and the scale 12 will be calibrated accordingly, but with a multiple cylinder engine the current impulses will be more frequent for the same speed and the scale will be calibrated difi'erently. The instrument can obviously be used in connection with an ignition magneto.

From the foregoing description taken in connection with the accompanying drawings, the advantages of the construction and method of operation will be readily understood by those skilled in the art to which the invention appertains, and while I have described the principle of operation, together with the device which I now consider to be the best embodiment thereof, Idesire to have it understood that the device shown is merely illustrative and that such changes may be made when desired as fall within the scope of the appended claim.

memes Having thus described my invention, ll claim as new and desire to secure by Letters Patent:

The combination with an ignition circuit of an internal combustion engine, of a revolution meter comprising an armature, a needle connected therewith, a field element magnetically related to the armature and composed of two oppositely-wound normally balanced coils each having a terminal connected with the ignition circuit, a resistance connected with vone coil, a reactance connected with the other coil, and the said resistance and reactance being-connected with the ignition circuit and of the same ohmic resistance, whereby the difierence in the flow of current through the coils will move the armature needle of the engine.

JOHN KIRBY.

to indicate the speed 

